Heat Pump Noise Levels: How Loud Are They Really?
One of the most common concerns about air source heat pumps is noise. Will it keep you awake? Will the neighbours complain? The honest answer: modern heat pumps at 42 dB are quieter than a fridge. But older or cheaper units can be noticeably louder. Here is what to expect, what the rules say, and how to keep noise to a minimum.
Heat pump noise at a glance
How loud is a heat pump compared to everyday sounds?
Decibels are hard to visualise, so here is how heat pump noise compares to sounds you already know:
The key thing to understand about decibels: they are logarithmic. A 10 dB increase sounds roughly twice as loud. So a 55 dB heat pump does not sound "a bit louder" than a 42 dB one — it sounds about three times louder. This is why choosing a quiet model matters.
🎧 Our honest take
Are heat pumps silent? No. You can hear them running, especially in a quiet garden on a still night. But a modern unit at 42 dB is a low hum — the kind of background noise you stop noticing after a few days. It is no louder than the fridge you already have in your kitchen. The noise concern is legitimate for older or cheaper units, but it should not put you off a quality installation.
When are heat pumps loudest?
Heat pump noise is not constant. It varies depending on what the unit is doing:
Coldest days (below 0°C)
LoudestThe compressor works hardest when it is coldest outside, which is exactly when you need the most heating. The unit runs at higher capacity and fan speed, producing more noise. Unfortunately, this also correlates with quiet winter nights when background noise is lowest.
Defrost cycles
NoticeableWhen ice forms on the outdoor unit (common in cold, damp weather), the heat pump runs a defrost cycle — briefly reversing the refrigerant flow to melt the ice. This can produce a brief whooshing or clicking sound lasting 2–5 minutes. It happens a few times a day in cold weather and is normal.
Mild weather / hot water only
QuietestIn spring and autumn, the unit runs at low capacity and is at its quietest. Many inverter-driven heat pumps modulate down to whisper-quiet levels when the heating demand is low.
Planning rules and noise limits
Air source heat pumps are generally permitted development — meaning you do not need planning permission — but only if the installation meets certain noise conditions.
Permitted development noise conditions
- MCS 020 compliance: The heat pump must not exceed 42 dB(A) at 1 metre from the nearest part of a neighbouring property that is a habitable room. This is assessed using the MCS 020 planning standard, which accounts for distance, barriers, and reflection.
- 1 metre from boundary: The unit must be at least 1 metre from the property boundary.
- Not on a balcony: Cannot be installed on a balcony, veranda, or raised platform.
- One unit only: Only one air source heat pump per property under permitted development.
If your installation cannot meet the 42 dB limit at the neighbour's boundary (for example, in a terraced house with a small garden), you will need full planning permission. This is not the end of the world — most councils approve heat pump applications — but it adds time and cost.
📐 How distance reduces noise
Sound drops by approximately 6 dB every time you double the distance from the source. So a heat pump producing 48 dB at 1 metre will be about:
Approximate figures. Actual reduction depends on ground type, barriers, and atmospheric conditions.
The quietest heat pumps available in the UK
If noise is a priority — and it should be if you have close neighbours — here are some of the quietest models currently available:
| Model | Noise (at 1m) | Output | Approx. cost (installed) |
|---|---|---|---|
| Vaillant Arotherm plus | 42 dB | 3.5–15.5 kW | £10,000–£14,000 |
| Samsung EHS Mono | 42 dB | 5–16 kW | £8,000–£12,000 |
| Daikin Altherma 3 | 44 dB | 4–16 kW | £9,000–£13,000 |
| Grant Aerona3 R32 | 44 dB | 6–17 kW | £9,000–£13,000 |
| Mitsubishi Ecodan | 45 dB | 5–14 kW | £9,000–£13,000 |
Noise levels from manufacturer datasheets (sound power at 1m, heating mode). Costs include installation but exclude the £7,500 Boiler Upgrade Scheme grant. Actual costs depend on property, system design, and installer.
All of these models are eligible for the £7,500 Boiler Upgrade Scheme grant, which brings the net cost down significantly. For more on heat pump costs and the grant, see our heat pump guide.
How to reduce heat pump noise
If noise is a concern — either for you or your neighbours — there are several practical steps to minimise it:
1. Choose a quiet model
The difference between 42 dB and 55 dB is enormous — it sounds about three times louder. Paying a bit more for a premium unit from Vaillant, Samsung, or Daikin is the single most effective thing you can do about noise.
2. Position it carefully
Place the unit as far from neighbouring bedrooms as possible. Avoid corners between walls, which amplify sound through reflection. A unit placed against a single flat wall is quieter than one tucked into an L-shaped corner. The MCS installer should model this using the MCS 020 noise assessment tool.
3. Use anti-vibration mounts
Rubber anti-vibration mounts between the unit and its base prevent vibration transferring into the ground or wall. This eliminates the low-frequency hum that is most noticeable indoors. Good installers include these as standard, but check.
4. Consider an acoustic enclosure
Purpose-built acoustic enclosures (like those from Quiet Air or similar) can reduce noise by 5–10 dB. They cost £500–£1,500 but can make the difference between meeting and failing the 42 dB planning limit. Ensure the enclosure allows adequate airflow — restricting airflow reduces efficiency and can damage the unit.
5. Never wall-mount if noise matters
Wall-mounted heat pumps transmit vibration directly into the building structure, which can cause a low hum audible inside the house. Ground-standing on a concrete plinth with anti-vibration mounts is always quieter. If wall-mounting is the only option, use heavy-duty vibration isolators.
What about neighbour complaints?
Let us be honest: some people do complain about heat pump noise. But the context matters.
Most complaints involve one or more of these factors:
- An older, noisier unit (pre-2020 models were significantly louder)
- Poor positioning (too close to a neighbour bedroom, in a corner that amplifies sound)
- Wall-mounting transmitting vibration into the building
- A unit oversized for the property, running inefficiently at high capacity
- Installation by a non-MCS installer who did not do a noise assessment
If your heat pump is properly installed by an MCS-certified installer, uses a modern quiet model, and meets the MCS 020 noise standard, the risk of a successful noise complaint is very low. Environmental health officers assess noise complaints against specific criteria, and a unit meeting MCS 020 is generally considered acceptable.
That said, being a good neighbour matters. If you are installing a heat pump, consider talking to your neighbours beforehand. Explain what it will sound like (show them a video of a modern unit running) and where it will be placed. A brief conversation prevents most disputes.
Ground source heat pumps: the silent alternative
If noise is a dealbreaker — for example, in a property with very close neighbours or in a quiet rural area where any mechanical sound stands out — a ground source heat pump is effectively silent outdoors. The compressor sits inside the house (typically in a plant room or utility), and the only outdoor component is underground pipes.
Ground source heat pumps are more expensive to install (£15,000–£35,000 before grants) but are more efficient and produce no outdoor noise at all. They qualify for the same £7,500 Boiler Upgrade Scheme grant. For more details, see our heat pump guide.
The bottom line on heat pump noise
Heat pumps are not silent. You will hear them. But a properly installed modern unit is no louder than a fridge, and most people stop noticing the sound within a week. The noise concern is valid for older or budget units, but the technology has improved dramatically — the quietest models today are 10 dB quieter than units from five years ago, which means they sound about half as loud.
If you are considering a heat pump, prioritise a quiet model, insist on proper positioning and anti-vibration mounts, and use an MCS-certified installer who will do a formal noise assessment. Get those things right and noise should not be a barrier.
Is a heat pump right for your home?
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Check your home →Sources
- MCS — MCS 020 Heat Pump Standard (noise assessment methodology)
- Energy Saving Trust — Air source heat pumps
- Planning Portal — Permitted development rights for heat pumps
- Manufacturer datasheets — Vaillant, Samsung, Daikin, Grant, Mitsubishi (2025/26 product lines)